portupgrade creates bogus messages

[[LoN]Kamikaze]

A portupgrade -a creates the following messages:

** Package 'e17-theme-milky' has been removed from ports tree.
** Package 'e17-theme-simply_white' has been removed from ports tree.
** Package 'e17-theme-gant' has been removed from ports tree.
** Package 'e17-theme-japan2007' has been removed from ports tree.

which are bogus, since these ports do exist. It's not an origin problem as
well, I portupgrade -f'ed them all.

The problem is entirely cosmetic so I didn't file a PR. Anyway, something seems
to be wrong. Does anyone have an idea what?